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| [GMCnet] Aerodynamics [message #249480] |
Mon, 12 May 2014 09:18  |
glwgmc
Messages: 1014
Registered: June 2004
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The owners of new Ford V10 powered small motorhomes about the size of ours would also "kill" for the 8-10 we get. According to FMCA articles they are getting around 6-7 with multi-speed transmissions, port FI, etc.
Jerry
Jerry Work
The Dovetail Joint
Fine furniture designed and hand crafted in the 1907 former Masonic Temple building in historic Kerby, OR
Visitors always welcome!
glwork@mac.com
http://jerrywork.com
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Message: 7
Date: Sun, 11 May 2014 22:44:19 -0600
From: Chris Tyler
Subject: Re: [GMCnet] Aerodynamics
To: gmclist@temp.gmcnet.org
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Content-Type: text/plain; charset="utf-8"
Compared to most SOB, esp those of ~40 yrs ago, the GMC is light years ahead of other makes in terms of aerodynamics. The stated CD of .031 is not at
all bad, howver the other factor is frotal area...which is rather large.
Lots of other class A owners would have killed for the 8-10 mpg we get, especially the old mopars.
Another factor is that drag goes up as a funtion of speed. In a NASCAR racer hitting 200mph, its a huge factor. If you are cruising at 50-60, I think
you would be hard pressed to see any measurable milage gain.
But a good running GMC CAN bury the speedometer, as I found out when I was young and foolish.
--
76 Glenbrook
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| Re: [GMCnet] AERODYNAMICS [message #362196 is a reply to message #249480] |
Thu, 04 February 2021 11:52  |
Olly Schmidt
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Location: Germany and Scottsville, ...
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On 04.02.21 18:45, Oliver Moore via Gmclist wrote:
> It would be easy to make a deflector to lessen air resistance--if it
> would improve mileage.
As the GMC MotorHome being fairly aerodynamic already, I doubt you will
see much improvement. Better make sure all the parts that are relevant
for optimal engine tuning are in place, you are not running any
unnecessary devices that consume energy, and you only travel with stuff
in your coach that you really need.
But I am sure others with real technical knowledge will chime in and
provide more insight.
--
Best regards
Olly Schmidt
PGP KeyID: 0x4196BF22
'76a 26' Eleganza II - Virginia, US
'73 23' Sequoia - Schleswig-Holstein, Germany
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Olly Schmidt
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'76a Eleganza II, VA
'73 Sequoia, SH, Germany
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| Re: [GMCnet] AERODYNAMICS [message #362199 is a reply to message #362196] |
Thu, 04 February 2021 12:54 |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
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Being that as an Aero Space Mechanical engineer does not qualify to do a
good evaluation ,
however I associate with an Engineer that does Practical Designs for
Formula cars in Europe.
He feels the rear is a major area that need to be addressed.
Basically he was telling me that a sharp corners will do wonders.
In my opinion I have a hard time seeing that.
On Thu, Feb 4, 2021 at 9:53 AM Olly Schmidt via Gmclist <
gmclist@list.gmcnet.org> wrote:
> On 04.02.21 18:45, Oliver Moore via Gmclist wrote:
>> It would be easy to make a deflector to lessen air resistance--if it
>> would improve mileage.
>
> As the GMC MotorHome being fairly aerodynamic already, I doubt you will
> see much improvement. Better make sure all the parts that are relevant
> for optimal engine tuning are in place, you are not running any
> unnecessary devices that consume energy, and you only travel with stuff
> in your coach that you really need.
>
> But I am sure others with real technical knowledge will chime in and
> provide more insight.
> --
> Best regards
>
> Olly Schmidt
> PGP KeyID: 0x4196BF22
> '76a 26' Eleganza II - Virginia, US
> '73 23' Sequoia - Schleswig-Holstein, Germany
>
> _______________________________________________
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>
--
Jim Kanomata
Applied/GMC, Newark,CA
jimk@appliedairfilters.com
http://www.gmcrvparts.com
1-800-752-7502
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Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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| Re: [GMCnet] AERODYNAMICS [message #362201 is a reply to message #362199] |
Thu, 04 February 2021 14:26 |
Randy Hecht
Messages: 93
Registered: March 2019
Location: Roswell, GA
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Sharp corners, perhaps causing laminar air flow similar to a golf ball dimple.
Randy Hecht
Roswell, GA
1974 Canyon Lakes GMC Motor-coach
> On Feb 4, 2021, at 13:55, Jim Kanomata via Gmclist wrote:
>
> Being that as an Aero Space Mechanical engineer does not qualify to do a
> good evaluation ,
> however I associate with an Engineer that does Practical Designs for
> Formula cars in Europe.
> He feels the rear is a major area that need to be addressed.
> Basically he was telling me that a sharp corners will do wonders.
> In my opinion I have a hard time seeing that.
>
>> On Thu, Feb 4, 2021 at 9:53 AM Olly Schmidt via Gmclist > gmclist@list.gmcnet.org> wrote:
>>
>>> On 04.02.21 18:45, Oliver Moore via Gmclist wrote:
>>> It would be easy to make a deflector to lessen air resistance--if it
>>> would improve mileage.
>>
>> As the GMC MotorHome being fairly aerodynamic already, I doubt you will
>> see much improvement. Better make sure all the parts that are relevant
>> for optimal engine tuning are in place, you are not running any
>> unnecessary devices that consume energy, and you only travel with stuff
>> in your coach that you really need.
>>
>> But I am sure others with real technical knowledge will chime in and
>> provide more insight.
>> --
>> Best regards
>>
>> Olly Schmidt
>> PGP KeyID: 0x4196BF22
>> '76a 26' Eleganza II - Virginia, US
>> '73 23' Sequoia - Schleswig-Holstein, Germany
>>
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>
>
>
> --
> Jim Kanomata
> Applied/GMC, Newark,CA
> jimk@appliedairfilters.com
> http://www.gmcrvparts.com
> 1-800-752-7502
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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| Re: [GMCnet] Aerodynamics [message #362236 is a reply to message #249480] |
Fri, 05 February 2021 17:01 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
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Hard to believe in the sharp rear corners being good. Like a basic semi trailer box. Companies like Trailer Tails have add on fold out baffles to eliminate the square edges to reduce drag
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: [GMCnet] Aerodynamics [message #362238 is a reply to message #249480] |
Fri, 05 February 2021 17:29 |
tphipps
Messages: 3005
Registered: August 2004
Location: Spanish Fort, AL
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My Ford V-10 powered Phoenix Cruiser averages 8.5 mpg while towing my 2010 Honda Fit. Without the toad, it moves up to near 9 mpg. Honda does not seem to hurt the mileage.
If I would slow down a little, I could improve mpg. I do find off the Interstate, mpg goes up due to slower speeds and not fighting drag.
Both my 1975 GMC Avions got about the same mileage.
2012 Phoenix Cruiser model 2552
KA4CSG
[Updated on: Fri, 05 February 2021 17:31] Report message to a moderator |
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| Re: [GMCnet] Aerodynamics [message #362240 is a reply to message #362238] |
Fri, 05 February 2021 17:38 |
sgltrac
Messages: 2797
Registered: April 2011
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My 2014 F550 rollback tow truck with the Triton v10 and 4 sp auto trans
never gets above 7. Usually 5 -6 mpg.
Sully
Bellevue wa.
On Fri, Feb 5, 2021 at 3:29 PM Thomas Phipps via Gmclist <
gmclist@list.gmcnet.org> wrote:
> My Ford V-10 powered Phoenix Cruiser averages 8.5 mpg while towing my 2010
> Honda Fit. Without the toad, it moves up to near 9 mpg. Honda does not seem
> to hurt the mileage.
> If I would slow down a little, I could improve mpg. I do find off the
> Interstate, mpg goes up due to slower speeds and not fighting drag.
> --
> 2012 Phoenix Cruiser model 2552
> KA4CSG
>
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Sully
77 Royale basket case.
Future motorhome land speed record holder(bucket list)
Seattle, Wa.
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| Re: [GMCnet] Aerodynamics [message #362244 is a reply to message #249480] |
Sat, 06 February 2021 16:52 |
6cuda6
Messages: 975
Registered: June 2019
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There might be something to the squarer back end claims....drive in the rain or wet roads and try to see out the rear window.
That being said i dont think more than about 10 mpg is gonna happen no matter unless yoir cruising on flat road, no wind, everything closed, no A/C, holding 62.5mph etc.....and maybe you might get q2....lol.
I always find it fumny when people talk MPG on a behicle....my thought is....if you wanna drive, it costs money, doesnt matter what the mpg is.
Rich Mondor,
Brockville, ON
77 Hughes 2600
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| Re: [GMCnet] Aerodynamics [message #362245 is a reply to message #362244] |
Sat, 06 February 2021 17:12 |
James Hupy
Messages: 6806
Registered: May 2010
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8 to 10 is about it. It's what I get with a carb equipped 26 foot Royale
with a 403. Anytime I push the speed up in the 75 mph range, it is a whole
bunch worse than that.
Jim Hupy
Salem, Oregon
On Sat, Feb 6, 2021, 2:52 PM 6cuda6--- via Gmclist
wrote:
> There might be something to the squarer back end claims....drive in the
> rain or wet roads and try to see out the rear window.
>
> That being said i dont think more than about 10 mpg is gonna happen no
> matter unless yoir cruising on flat road, no wind, everything closed, no
> A/C,
> holding 62.5mph etc.....and maybe you might get q2....lol.
>
> I always find it fumny when people talk MPG on a behicle....my thought
> is....if you wanna drive, it costs money, doesnt matter what the mpg is.
> --
> Rich Mondor,
>
> Brockville, ON
>
> 77 Hughes 2600
>
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| Re: [GMCnet] Aerodynamics [message #362253 is a reply to message #362244] |
Sat, 06 February 2021 22:46 |
rallymaster
Messages: 662
Registered: February 2004
Location: North Plains, ORYGUN
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Sort of on subject...no square ends, but great mileage.
I got over 11mpg on some of the segments of my homeward trip from
Pittsburgh after picking up my 23 footer. Coming across flat-lands with
one (or 2 or 3 or more) hellacious tailwinds.
Ron Clark
On 2/6/2021 2:52 PM, 6cuda6--- via Gmclist wrote:
> There might be something to the squarer back end claims....drive in the rain or wet roads and try to see out the rear window.
>
> That being said i dont think more than about 10 mpg is gonna happen no matter unless yoir cruising on flat road, no wind, everything closed, no A/C,
> holding 62.5mph etc.....and maybe you might get q2....lol.
>
> I always find it fumny when people talk MPG on a behicle....my thought is....if you wanna drive, it costs money, doesnt matter what the mpg is.
--
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Ron & Linda Clark
North Plains, ORYGUN
78 Eleganza II
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| Re: [GMCnet] Aerodynamics [message #362261 is a reply to message #249480] |
Sun, 07 February 2021 10:25 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
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My record was 12 (11.98something) driving the freeway homefrom Asheville. Freeway the whole way,downhill the whole way, and cruise set at 55. I was trying. Normally, about 9 in the 26' bobtail, a bit over 8 with a toad behind.
==johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: [GMCnet] Aerodynamics [message #362273 is a reply to message #249480] |
Sun, 07 February 2021 15:40 |
kingd
Messages: 592
Registered: June 2004
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to James Hupy. Re Canadian Gasoline. I believe for all brands in Toronto they now all contain Ethanol EXCEPT the Premium 91 Octane.
A lot of pumps are labelled like this On the 87 Octanc may contain up to 10% Ethanol, the 89 Octane may contain up to 5% Ethanol
and on the 91 Octane Contains No ethanol. We also have 93 and 94 octane I believe they get this by adding Ethanol to the Ethanol
free 91 Octane as the 93 and 94 do contain Ethanol. It is expensive to use the 91 just to avoid Ethanol in a vehicle that really doesn't care.
I keep planning to do some back to back long distance comparison with 87 Octane and 91 but it never works out. My 2007 Dodge Grand Caravan
3.8 L motor doesn't seem to care. If I get the motorhome back on the road maybe I can get more performance info.
DAVE KING
lurker, wannabe
Toronto, Ontario, Canada
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| Re: [GMCnet] Aerodynamics [message #362291 is a reply to message #362273] |
Mon, 08 February 2021 16:37 |
James Hupy
Messages: 6806
Registered: May 2010
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Guess things have changed a bit since we drove our coaches trans-canada a
few years ago. We only used fuel from one major supplier, and always got
the alcohol free fuel . At that time, you could pick your octane
requirement. We used 88 octane during the whole trip. I believe the brand
was Petro-Canada. As soon as we returned stateside, our mileage dropped 15
to 20 % over what we were getting in Canada and the old vapor lock symptoms
returned as well. Some of our travels were in the Canadian Rockies and the
Altitude reached 10,000 feet in some places. No knocks, no pings, no
nothing.
Jim Hupy
Salem, Oregon
On Sun, Feb 7, 2021 at 1:41 PM Dave King via Gmclist <
gmclist@list.gmcnet.org> wrote:
> to James Hupy. Re Canadian Gasoline. I believe for all brands in Toronto
> they now all contain Ethanol EXCEPT the Premium 91 Octane.
> A lot of pumps are labelled like this On the 87 Octanc may contain up to
> 10% Ethanol, the 89 Octane may contain up to 5% Ethanol
> and on the 91 Octane Contains No ethanol. We also have 93 and 94 octane I
> believe they get this by adding Ethanol to the Ethanol
> free 91 Octane as the 93 and 94 do contain Ethanol. It is expensive to use
> the 91 just to avoid Ethanol in a vehicle that really doesn't care.
>
> I keep planning to do some back to back long distance comparison with 87
> Octane and 91 but it never works out. My 2007 Dodge Grand Caravan
> 3.8 L motor doesn't seem to care. If I get the motorhome back on the road
> maybe I can get more performance info.
> --
> DAVE KING
> lurker, wannabe
> Toronto, Ontario, Canada
>
> _______________________________________________
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| Re: [GMCnet] Aerodynamics [message #362293 is a reply to message #362291] |
Mon, 08 February 2021 17:33 |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
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One need to fill at least 5 times to get a close figure as it will vary
each time you fill up.
One tankfull is not worth using to obtain any worthwhile milage calculation.
On Mon, Feb 8, 2021 at 2:38 PM James Hupy via Gmclist <
gmclist@list.gmcnet.org> wrote:
> Guess things have changed a bit since we drove our coaches trans-canada a
> few years ago. We only used fuel from one major supplier, and always got
> the alcohol free fuel . At that time, you could pick your octane
> requirement. We used 88 octane during the whole trip. I believe the brand
> was Petro-Canada. As soon as we returned stateside, our mileage dropped 15
> to 20 % over what we were getting in Canada and the old vapor lock symptoms
> returned as well. Some of our travels were in the Canadian Rockies and the
> Altitude reached 10,000 feet in some places. No knocks, no pings, no
> nothing.
> Jim Hupy
> Salem, Oregon
>
> On Sun, Feb 7, 2021 at 1:41 PM Dave King via Gmclist gmclist@list.gmcnet.org> wrote:
>
>> to James Hupy. Re Canadian Gasoline. I believe for all brands in Toronto
>> they now all contain Ethanol EXCEPT the Premium 91 Octane.
>> A lot of pumps are labelled like this On the 87 Octanc may contain up to
>> 10% Ethanol, the 89 Octane may contain up to 5% Ethanol
>> and on the 91 Octane Contains No ethanol. We also have 93 and 94 octane I
>> believe they get this by adding Ethanol to the Ethanol
>> free 91 Octane as the 93 and 94 do contain Ethanol. It is expensive to
> use
>> the 91 just to avoid Ethanol in a vehicle that really doesn't care.
>>
>> I keep planning to do some back to back long distance comparison with 87
>> Octane and 91 but it never works out. My 2007 Dodge Grand Caravan
>> 3.8 L motor doesn't seem to care. If I get the motorhome back on the road
>> maybe I can get more performance info.
>> --
>> DAVE KING
>> lurker, wannabe
>> Toronto, Ontario, Canada
>>
>> _______________________________________________
>> GMCnet mailing list
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>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>
> _______________________________________________
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--
Jim Kanomata
Applied/GMC, Newark,CA
jimk@appliedairfilters.com
http://www.gmcrvparts.com
1-800-752-7502
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Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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| Re: [GMCnet] Aerodynamics [message #362298 is a reply to message #362293] |
Mon, 08 February 2021 19:38 |
 |
Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
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jimk wrote on Mon, 08 February 2021 18:33One need to fill at least 5 times to get a close figure as it will vary each time you fill up.
One tankfull is not worth using to obtain any worthwhile milage calculation.
In the time I was getting to know Chaumière, I would sample all the fuel we bought. I would use a modified version of KenB's alcohol measurement and would that with the other data. When the fill vent and vapor valve got fixed, I could see the alcohol content in the fuel almost exactly as reduced mileage (increased fuel rate). The only scatter was cause by the overlap of different fuel quality. It was otherwise very consistent.
For the most part, I would agree with you Jim(K), but we have had a working vapor valve and the modified fill vent for a while, so I can take on fuel to with better than normal consistency. When I did the overhaul in 2018, I was very concerned that I would be back to the 9.2 that I count on. I drove the new engine about 190 miles around town (I wanted to be over 200). Then we took off for Ankeny/Amana and the fall international. That was just short of 1200miles. We were home long enough to answer the mail and wash some clothes before we made of Albany a class reunion for Mary. That was a little over 1300 miles with the stops to visit friends and family.
This applies in this case because I log each fuel stop mileage, fill and cost. Each got better as the new parts (lots of new parts) settled in. Half way across NY, that fill came up to total since departure on September 18 to October 03 and about 2000 Miles of 9.1. With the last fill on the backhaul which included so doodle-bopping in Albany we were back to 9.3 with a standard deviation of less that 0.2MPG. That is about the deviation I usually see and it is about a 3% which is also the deviation I see between our odometer and the GPS trip log. Unfortunately, the actual logs of those mentioned excursions were lost with the hard drive crash on the way home from Tallahassee.
Then again... Thinking can be dangerous. I only just now figured out that I can rebuild that fuel consumption from the fuel slips that are probably waiting for me on the visor of Chaumière. Every fuel stop, I write the mileage on the fuel slip(s). The date and location is already on there.
So, I believe that JimH could detect that alcohol content.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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